1. Field of the Invention
The present invention relates to a laser processing method, an ink jet recording head, and a system for manufacturing ink jet recording heads.
2. Related Background Art
In recent years, a laser oscillator has been widely used as a light source for a laser processing system. Particularly, a pulse laser oscillator whose range is beyond ultraviolet has attracted attention as a light source for the performance of polymer patterning abrasion without any development process.
As a laser processing method or a laser processing system that processes polymer by the utilization of abrasion, the one, which is provided with a laser light source unit and specific patterns, is proposed. It is further provided with a mask unit having the mask that allows laser beams to be transmitted from the laser light source unit to the work side through the mask; a projection optical system that projects the laser beams from the laser light source unit; and a measurement and movement system that measures the work positions and moves the work accordingly (such as disclosed in the specifications of Japanese Patent Laid-Open Application No. 4-9291 and Japanese Patent Laid-Open Application No. 4-339585).
A laser processing method of the kind is mainly used for minute processing of ink jet openings of an ink jet recording head (see Japanese Patent Laid-Open Application No. 2-121842, Japanese Patent Laid-Open Application No. 2-187346, Japanese Patent Laid-Open Application No. 3-101954, and Japanese Patent Laid-Open Application No. 3-101960), and used for processing ink flow paths of an ink jet recording head (see Japanese Patent Laid-Open Application No. 2-121845) among some others.
The ink jet recording head referred to in this application is adopted particularly for the recording head of bubble jet type among those using the ink jet recording method. The typical structure and operational principle of such method are disclosed in the specifications of U.S. Pat. Nos. 4,723,129 and 4,740,796, for example. This method is applicable to the so-called on-demand type recording system and a continuous type recording system as well. To describe this method in regard to the on-demand type, for example, each of electrothermal transducing devices is arranged for a sheet or a liquid path (ink flow path) that retains liquid (ink), and such electrothermal transducing device is caused to generate thermal energy in accordance with driving signals, thus creating film boiling on the thermal activation surface of a recording head. As a result, each bubble is formed in liquid (ink) one to one in response to each of the driving signals described above. By the development and contraction of each bubble thus created, the liquid (ink) is discharged through a discharge opening in the form of a droplet. The driving signal is more preferably in the form of pulses such as disclosed in the specifications of U.S. Pat. Nos. 4,463,359 and 4,345,262. Also, it is preferable to adopt the temperature increasing rate of the heating surface as disclosed in the specification of U.S. Pat. No. 4,313,124.
The structure of the recording head described above is arranged by combining the ink discharge openings (orifices), linear or right-angled liquid paths (ink flow paths), and electrothermal transducing devices as shown in each of the above-mentioned specifications. Besides, the structure such as disclosed in the specifications of U.S. Pat. Nos. 4,558,333 and 4,459,600 wherein the thermal activation portions are arranged in a curved area may be arranged. In addition, the ink jet recording head described above may be structured as disclosed in Japanese Patent Laid-Open Application No. 59-123670, for example, wherein a common slit is used as the discharging ports for plural electrothermal transducing devices, or as disclosed in Japanese Patent Laid-Open Application No. 59-138461, for example, wherein an aperture for absorbing pressure wave of the thermal energy is formed corresponding to the discharge openings. Here, the ink jet recording heads disclosed in the above specifications are arranged to secure a length that corresponds to a specific width by the combination of plural recording heads. However, it may be possible to arrange the structure so that one recording head is able to deal with a length that corresponds to a specific width (that is, the maximum recordable width of a recording medium that a recording apparatus can handle).
Also, the structure of the ink jet recording head described above may be of an exchangeable chip type or cartridge type provided for the recording head itself, where the head is electrically connected with the apparatus main body (for the operation of the electrothermal transducing devices), and ink is then made suppliable as well.
When a laser processing is executed for the formation of fine grooves such as ink flow paths with respect to the part (work) of an ink jet recording head of the kind, it takes a time for the conventional laser processing method to complete such execution if the grooves are configured three-dimensionally with irregularities in the direction of laser irradiation.
For example, if the configuration of the grooves is three-dimensional such as to confine the supply force of ink toward only the opening side or to provide an extrusion on the midway of each groove to present resistance to the flow of ink, the grooves cannot be formed three-dimensionally by a one-time processing. Here, using two or more kinds of masks a multiple processing should be executed. It requires such processing to take a time so that a problem of lowered productivity should arise.
Further, for the processing at the second time and on, the work should be positioned exactly as it has been positioned for the first processing. This positioning requires a higher precision of the image process to be performed for positioning, as well as for each stage of a work movement system. This requirement naturally brings about a problem that the processing system itself should be built in a larger scale.
When processing the three-dimensional grooves, it is of course possible to adopt a dielectric mask so that a certain percentage of laser beams can be transmitted for processing. However, the dielectric mask itself is expensive, and the 100% reflectance of the laser cannot be obtained, either. Further, it is extremely difficult to form fine and highly precise patterns on the dielectric mask itself. As a result, there is automatically a certain limit in utilizing the dielectric mask.